Remotely controlling a rover on Mars can get a little bit complicated. Scientists and engineers must make thousands of decisions every day on what types of data to collect, what information to transmit back to Earth and where to guide the intrepid explorer next.
This is an implementation of the NASA Mars24 Sunclock algorithm developed by Dr. Michael D Allison, using the R programming language. For more information, see: Allison, M. Accurate analytic representations of solar time and season on Mars with applications to the Pathfinder/Surveyor missions. Mars24 requires a computer with Java 9 (or later version) installed. The current version of Mars24 is 8.2.1, released 2021-03-30. Download Mars24 8.2.1 for macOS, 35 MB DMG Download Mars24 8.2.1 for Windows, 32 MB ZIP.
On top of all this, they must keep track of something most of us rarely consider: the time on Mars. Knowing exactly when afternoon arrives for a particular rover—either Opportunity, which landed in 2004 and is still in operation, or Curiosity, which arrived to great fanfare earlier this week—is crucial for its operators, since that is when data is uploaded from the craft and sent back to Earth.
The Mars 2020 Perseverance mission lifted off from Cape Canaveral, Florida, on July 30. NASA's Eyes on the Solar System tool lets you track the spacecraft in real time as it makes its way to Mars for a Feb. 18, 2021, landing.
“The rover downlink, in the afternoon on Mars, is what we use to plan the next day’s activities for the rover,” says Smithsonian scientist John Grant, who works on daily geologic data collection as well as long-term planning for the mission. “So we are tied to the time of the downlink and when the uplink of the commands will occur the next morning.”
The problem is that Mars has a 24-hour and 39-minute day, so its time zones don’t match up with any on Earth. Unlike, say, East Coast residents simply remembering to subtract three hours to know the time on the West Coast, scientists must keep track of a constantly varying difference between time zones. ”It’s confusing to keep track of two different times, especially when you are used to living on one time and working on another that keeps shifting,” Grant says.
See what Maria Campos (mars24) has discovered on Pinterest, the world's biggest collection of ideas. Mars24 is a Java program and browser applet which displays a Mars 'sunclock', a graphical representation of the planet Mars showing its current sun- and nightsides, along with a numerical readout of the time in 24-hour format.
Thankfully, there’s an app for that.
NASA has produced a free Java application called Mars24 that provides the exact times for a number of places on the Red Planet, including the current location of Opportunity (a.k.a. MER, the Mars Exploration Rover ), Curiosity (a.k.a. MSL, the Mars Science Laboratory) and even the immobile Viking 1 lander, which has been out of operation since 1982. You can also alter the settings to see the time at given Martian landmarks, such as Olympus Mons, the tallest mountain on any planet in the Solar System.
The app also includes a visual representation of Mars called a sunclock, which shows a map of which parts of the planet are currently light and dark.
Mars24 is available for Mac OS X, Windows and Linux. If you want to have a handy way to check the time on your smartphone, you’ll have to opt for a non-NASA app, such as Mars Clock or Mars Surface Times, both available in the App Store for iPhone, or Martian Time, available at Google Play for Android.
Of course, Mars24 is fun for members of the public interested in following Curiosity, but the pros have their own ways of keeping track of Martian time. Grant says that the software which shows his daily schedule of meetings and Mars-related events expresses each entry in both Earth and Mars times. Additionally, when working on the previous rovers Spirit and Opportunity, he and other members of the team wore special watches that actually ran on Martian time. (His watch is on view in the Air and Space Museum if you’d like to check the time for yourself.)
One technical aspect to note is that although a Martian day is actually longer than 24 hours, the convention is still to express the time there in terms of a 24 hour period for convenience. To do so, scientists simply divide the actual duration of a Martian day by 24 to calculate the length of a Martian hour, and divide that by 60 for the length of a Martian minute, and so on. So a Martian hour is slightly longer than an Earth hour, and a Martian minute slightly longer than an Earth minute. All in all, pretty otherworldly.
Mars24 algorithm
Mars Calendar and orbit calculation based on Allison and McEwan (2000), Allison (1997)
Allison, M., and M. McEwen 2000. A post-Pathfinder evaluation of aerocentric solar coordinates with improved timing recipes for Mars seasonal/diurnal climate studies. Planet. Space Sci. 48, 215-235
Allison, M. 1997. Accurate analytic representations of solar time and seasons on Mars with applications to the Pathfinder/Surveyor missions. Geophys. Res. Lett. 24, 1967-1970.
Returns the Mars Year date based on the reference date from Clancy(2000): 1955 April 11, 11am
The Mean Solar Time at the Prime Meridian
Returns the Fictional Mean Sun angle
The Local Mean Solar Time given a planetographic longitude
Local true solar time is the Mean solar time + equation of time perturbation
Returns the Areocentric solar longitude (aka Ls)
Calculates the Mars Mean Anomaly given a j2000 julian day offset
Return the Mars Solar date
Returns the Mars Year date based on the reference date 1955 April 11, 10:56:31 mtc after finding the j2k offsets of the zeroes of the Mars_Ls function.
Returns the perturbations to apply to the FMS Angle from orbital perturbations
Interface, calls west_to_east to convert longitude
The true anomaly (v) - the Mean anomaly (M)
Equation of Time, to convert between Local Mean Solar Timeand Local True Solar Time, and make pretty analemma plots
Instantaneous orbital radius
Heliocentric Latitude, which is not Ls
Heliocentric longitude, which is not Ls (offsets are different)
Hourangle is the longitude - subsolar longitude
Returns the j2000 epoch as a float
What Time Is It On Mars
Returns j2000 based on MSD
Returns the julian day offset since the J2000 epoch
Returns j2000 offset based on MSD
Returns the julian day number given milliseconds since Jan 1 1970
Returns the TT Julian day given a UTC Julian day
Returns the current time in milliseconds since Jan 1 1970
Azimuth Angle, between sun and north pole
Mars24
Returns the solar declination
Elevation = 90-Zenith, angle between sun and flat surface
Zenith Angle, angle between sun and nadir
returns the longitude of the subsolar point for a given julian day.
Returns the offset in seconds from a julian date in Terrestrial Time (TT)to a Julian day in Coordinated Universal Time (UTC)
Returns the offset in seconds from a julian date in Terrestrial Time (TT)to a Julian day in Coordinated Universal Time (UTC) [MATH]
Returns the offset in seconds from a julian date in Terrestrial Time (TT)to a Julian day in Coordinated Universal Time (UTC) [NUMPY]
Mars Clock Program
Convert from west longitude to east longitude,or vice versa.